Cellulose ethers have widespread applications as membranes in, e.g., dialysis, reverse osmosis and ultrafiltration. More recently, membranes and hydrogels comprising cellulose have been investigated for use in the controlled release of fertilizers and pesticides in agriculture. To provide improved service life and higher strength, cellulose ether membranes are often cross-linked. Current processes for cross-linking cellulose ethers typically require potentially toxic catalysts such as organotin or organozinc compounds, high heat, and/or high pressure.